This invention relates to a receiving and transmitting combination for electromagnetic radiation beams in the optical portion of the electromagnetic spectrum, and more particularly to such a device for use in optical information transmission systems.
Optical information transmission has been hampered in the past by range limitations imposed due to rapid dissipation of the optical information in transit from a transmitter to a receiver. High ambient optical radiation background further hampers reception and causes the problem of discriminating between background radiation and transmitted electromagnetic radiation information. Certain applications for transmission of electromagnetic radiation in the optical portion of the spectrum present circumstances where running lengths of electrical cabling is inconvenient or impractical. Further, transmission of information optically is limited to line of sight and objects opaque to the transmitted radiation prevent information flow. Therefore, apparatus and method are desirable for extending the range of transmitted optical information in the presence of high ambient optical radiation background, as well as apparatus and method eliminating cabling and allowing redirection of transmitted optical radiation en-route to its ultimate destination.